Compliance roll

ABSTRACT

A compliance roll structure suitable for use in processing a web of film within a thermal developing cavity. The roll is adapted to accommodate for a change in the web geometry caused by one curved surface of the developing cavity being brought into contact therewith. The compliance roll delivers a constant load to the film thus placing the film under a uniform tension during development.

United States Patent 1 1 1111 3,851,839 Hynes Dec. 3, 1974 COMPLIANCE ROLL 3,177,795 4/1965 Stewart 95/89 R x 3,223,824 l2/l965 Shaler ct ul [751 Inventor: Frank Hynes, Rochester 3,739,143 6/1973 Amundson ct 111 95/89 R x [73] Assigneez Xerox Corporation, Stamford 3,757,081 9/1973 Smith et 11] 219/216 Conn, Primary E.\'aminer-Fred L. Braun [22] Flled: Sept 1973 Attorney, Agent, or FirmRobert J. Bird 21 Appl. No.: 399,590

[57] ABSTRACT 52 us. c1 242/147 R, 226/195, 242/753 A eemplianee l strueture Suitable fer use in 51 1m. (:1 B65h 59/00 eessing a web of film Within a thermal developing [58] Field 61 Search 95/89 A, 89 R, 94 R; y- The Yell is adapted to accommodate for a change 219/21 3 22 /113 1 4 195; 432 59 in the web geometry caused by one curved surface of 225; 242/753 147 354/297 299 the developing cavity being brought into contact therewith. The compliance roll delivers a constant 5 References Cited load to the film thus placing the film under a uniform UNITED STATES PATENTS tension during development.

3,038,994 6 1962 M81566 H 61...; 219/388 ux 5 Claims, 3 Drawing Figures COMPLIANCE ROLL This invention relates to a compliance roll structure and, in particular, to a compliance roll capable of delivering a constant uniform load against a web of film as the geometry of the web is changing.

In recent years, many types of films have been developed which, upon exposure to a light image, can be developed by simply heating the film to or above the predetermined developing threshold temperature of the emulsion contained herein. Broadly, this type of film is referred to as dry film and is exemplified by a silver halide based film as disclosed in US. Pat. No. 3,455,075. I-leretofore, most dry films have been processed in the form of cut strips with each strip containing a single exposure or frame thereon. Efforts to automate the developing process whereby a continuous web of film containing a plurality of exposures is moved through a thermal zone has heretofore proven difficult. The film material is subject to heat induced shrinkage problems due to the relatively high developing temperatures involved whereby a thermal gradient is established in the film boundary regions adjacent to the development zone. As a consequence, internal stresses are produced in the film which are manifested in the form of a series of wrinkles. The amplitude of wrinkling is found to be proportional to the intensity of the heat induced stresses. These wrinkles, if not corrected, seriously effect the density of the images processed.

To counteract or offset this wrinkling problem, a contact type heating system has been devised which employs a curvilinear platen having a radius of curvature specifically designed to relieve the stresses produced in the film. This developing system is the subject matter of copending U.S. patent application S.N. 377,888 filed July 9, 1973 in the name of Thompson. By placing a constant or uniform tension upon the film and while it is in contact withthe curved platen surface, a normal force, which varies in proportion to the amplitude of film deformation, is exerted upon the film during development which relieves the wrinkle inducing stresses therein. The density of the images thus developed are brought well within the limits needed to produce high quality image renditions.

As can be seen, the geometry of the web is constantly changed as the curved platen surface is brought into contact with the film. Under normal operating conditions, that is, with the film in a looped configuration and both ends of the loop secured, the tension on the film will change as the geometry of the loop configuration changes. It has therefore been found difficult to maintain the required uniform tension upon the web required for high density image development.

It is therefore an object of the present invention to apply uniform tension on a web of material as the web geometry is changing.

It is a further object of the present invention to facilitate processing of a web of dry film.

It is yet another object of the present invention to provide a compliance roll structure for delivering a uniform tension to a web of dry film during periods when the geometry of the film is changing.

A yet further object of the present invention is to develop automatically images of uniform density in a repeatable manner upon a continuous web of dry film.

These and other objects of the present invention are attained by means of a thermal developing system for processing a web of dry film, the developing system having a curved platen surface adapted to move into contact with a portion of the continuous web within a development zone and a compliance means for exerting a uniform tension upon the film as the geometry of the film changes to accommodate the curved platen surface.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:

FIG. I is a side view of the processor illustrating the developing means contained therein in an open posi tion and a compliance means acting on the web in an extended condition;

FIG. 2 is similar to FIG. 1 and illustrates the developing means in a closed position against the web of film and further illustrating the compliance means in a retracted condition; 9

FIG. 3 is an end view illustrating the developing means in a closed position with the film removed.

Referring now more specifically to the drawings, there is shown a continuous web of dry film 9 being drawn through a thermal developing station,generally referenced 10. Although not shown, the web is previously imaged downstream from the development station so that a series of exposures or frames are recorded upon the emulsion side of the film prior to the film entering the developing station. The developing station .is basically made up of a fixed lower platen 12, secured to a base plate 13 by means of bolts 14, and a movable upper platen 15. As noted in the previously mentioned Thompson application, the upper platen is provided with a curved heated working surface adapted to move into and out of physical contact with the back side or non-emulsion side of the film. The working surface of the lower platen is formed to complement that'of the upper platen. When the upper platen is seated in contactwith the film in a developing position as shown in FIG. 2, the lower platen surface is positioned in noncontiguous close proximity with the emulsion side of the film.

As described in greater detail in US. Pat. application S.N. 377,887, filed in the name of May, July 9, 1973, the upper and lower platen surfaces are both electrically heated under controlled conditions whereby the working surfaces on both platens are elevated to the same temperature. The working temperature of the system is at or preferably above the threshold developing temperature of the film in process. As a result, when the cavities are brought together into thermal communication with the web of film, the upper platen serves to rapidly heat the film to the desired developing temperature by a conductive heat transfer mechanism. Because of the equal temperatures maintained at the platen working surfaces, the film continues to be heated under adiabatic steady state conditions until the developing process is complete.

By utilizing a conductive heat transfer mechanism under transient conditions 'and a steady state adiabatic process under steady state conditions, the developing system is capable of developing high density images while still being provided with a wide latitude of developability.

As best illustrated in FIG. 3, the upper or movable platen 15 of the developing system is mounted upon a yoke made up of a horizontal bracket 17 which is supported in parallel spaced relation with the base plate 13 by means of vertical spacers 18 carried upon the base. The main body 20 of a solenoid Sol-l is affixed to the upper surface of the horizontal bracket with the movable solenoid shaft 21 being arranged to pass downwardly through an opening provided within the bracket. The upper platen is secured, as for example by pinning, to the free end of the solenoid shaft and is adapted to move therewith.

A pair of circular guide rods 23 are also affixed to the outboard ends of the upper platen and are slidably .mounted within bushings 24 pressed into bracket 17. A

compression spring 25 is operatively attached to the guide rods via a retaining ring 26 whereby the upper platen is continually urged or biased upward into an open position as shown in FIG. 1. Normally, the solenoid is held in an energized condition to hold the developing cavity closed. During indexing of the film through the system, the solenoid is periodically deenergized causing shafts 21, and thus the upper platen attached thereto, to be raised opening the developing cavity (H6. 1). The guide rods and bushings are arranged to direct the movable upper platen along a path of travel which is substantially perpendicular to the plane of base plate 13.

The film width 9 is drawn intermittently through the developing station between a supply spool and a take up spool (not shown). A pair of coacting pinch rolls 40, 41 act upon the web at the entrance to the developing station. An electromagnetic clutch 43 is operatively connected to the upper pinch roll and acts, through an appropriate control network, to lock the pinch roll in an inactive condition when the upper platen is moved into contact with the web of film, that is, during the developing phase of the operation. Sufficient pres sure is exerted by the coacting rolls against the film, when in the locked position, to hold the downstream portion of the web immobile during closure of the developing cavity. The web of film within the developing station is trained over a series of idler rolls 45, 46, 47 and a compliance roll structure 50, the function of which will be explained below. At the exit to the developing station is positioned a second pair of pinch rolls 72, 73 adapted to rotate in the web advancing direction only. The web is tracked around the lower pinch roll 73 so that sufficient contact is made with the web to prevent the upstream portion of the web from moving back into the developing station. As a consequence, both ends of the web passing through the developing station are held secure during development. Generally, a 90 contact region is sufficient to produce this desired result.

As can be seen from FIG. ll, when the developing cavity is held is an opened position, i.e., when the solenoid is energized, a straight run of film is established between idler rolls 46, 47 which extends through the thermal development zone. At this time, the pinch rolls positioned at the entrance and exit of the developing station are in a locked position so that a finite length of film is contained therebetween. Bringing the curved platen surface into intimate contact against the straight run of the film, as for example when the platen is brought into the closed position as illustrated in FIG. 3, causes the geometry of the film web or loop within the developing station to become altered.

To allow for changes in the web geometry to accommodate the curved platen surface, there is herein provided a compliance roll structure, generally referenced 50'. The compliance roll structure includes a cylindrical roller 51, formed of metal or plastic, and a metallic support shaft 52 upon which the cylinder is mounted. The outboard ends 54 of the shaft 52 extend beyond the roller cylinder and are arranged to ride within slotted holes 55 formed in a pair of support frames 57, 58 mounted within the developing station. In assembly, the run of web extending between the cooperating pinch rolls 72, 73 and idler roll 47 is such that the surface of the compliance roller 51 is capable of contacting the back side of the film over the rolls freedom of movement within the slotted holes.

A pair of spring members 61 are operatively attached to the extreme ends of the compliance roller support shaft via pins 59. The springs are basically constant compression springs which are made up of helix wound coil 61 and terminating at each end in trunions 62, 63. Trunion 62 of each spring is wrapped about a support pin stacked in the support frame while trunions 63 are wrapped around the previously noted pin 59 se cured in the compliance roll support shaft. Each spring is supported between the pins 59, 65 in a loaded condition so that the compliance roller surface is biased or urged continually against the back side of the film. As the geomerty of the web loop is changed, as for example by closure of the developing cavity, the position of the compliance roller within the slotted holes is altered to accommodate for changes in the web geometry thus preventing the film from being broken or otherwise harmed.

As pointed out in the previously noted Thompson application, it is necessary in this type of developing system, because of the heat transfer mechanisms involved, to hold the film against the curved platen surface under a substantially constant and uniform tension. The compliance roll structure of the present invention, through the biasing spring arrangement, delivers a uniform load against the film loop regardless of the positioning of the roller within the slotted holes provided. The constant compression springs herein utilized are specifically designed to deliver a constant biasing force against the film material over the entire deflection or working range thereof. In operation, as the spring is being flexed, the amount that the external diameter of the helix is being reduced in regard to the trunion ends of the spring is just sufficient so that the separation provided between the coils is substantially equal for various degrees of compression. Although the leverage, which tends to separate the coils of the helix, is greater at the center portion of the spring, the resistance to separation becomes less at the ends so that equal separation is obtained. For further details concerning this type of spring construction, reference is herein had to US. Pat. Re. No. 23,974 filed in the name of Foster.

in practice, the compliance roll structure moves towards the right, as illustrated in F168. 1 and 2, when the developing cavity is placed in an open position. Upon closure of the cavity, wherein the length of web between the locked pinch rolls is held finite, the compliance roll is urged back by the film against the biasing force of the spring. This movement of the compliance roll structure shortens the run distance between the coacting pinch rolls 72, 73 and idler roll 47 thus automati cally providing extra film needed to accommodate the curved platen surface. At the same time, the spring is being deflected. However, because of its design, the springs continually translate a uniform tensioning force upon the web thus holding the web against the upper platen surface under a uniform load. The spring force is preset so that the film is held in intimate contact with the platen during development with sufficient loading to maintain good contact but with insufficient force to stress the film beyond its elastic limits during the thermal heating process.

While this invention has been described with reference to structure disclosed herein, it is not confined to the details set forth and this application is intended to cover any modifications or changes as may come within the scope of the following claims.

What is claimed is:

1. In apparatus for processing a web of film having a developing system including a curvilinear surface adapted to move into contact with said film whereby the film is tensioned against said curvilinear surface,

a compliance roll movably positioned between said curvilinear surface and one of said film securing means whereby said compliance roll contacts said film, said compliance roll being arranged to move in compliance with the change in the film loop geometry caused by the curvilinear surface moving into contact with said film,

bias means operatively associated with said compliance roll for tensioning said roll under a constant load against said film throughout the range of roll movement,

said bias means including a compression spring of substantially constant compression force throughout its displacement.

2. The apparatus of claim 1 wherein said film has an emulsion on one side thereof and said compliance roll is adapted to contact the side of said film opposite said emulsion.

3. The apparatus of claim 1 wherein said film is adapted to be indexed in a frame by frame sequence through said developing system.

4. The apparatus of claim 3 wherein said roll is adapted to move in a direction substantially normal to the path of travel of said film.

5. The apparatus of claim 1 wherein said compression spring comprises a helix spring member. 

1. In apparatus for processing a web of film having a developing system including a curvilinear surface adapted to move into contact with said film whereby the film is tensioned against said curvilinear surface, the improvement comprising means to secure said film on both sides of said developing system to form a fiLm loop of predetermined length therebetween having at least one straight run thereon, means to place said curvilinear surface into contact with said film along said straight run, a compliance roll movably positioned between said curvilinear surface and one of said film securing means whereby said compliance roll contacts said film, said compliance roll being arranged to move in compliance with the change in the film loop geometry caused by the curvilinear surface moving into contact with said film, bias means operatively associated with said compliance roll for tensioning said roll under a constant load against said film throughout the range of roll movement, said bias means including a compression spring of substantially constant compression force throughout its displacement.
 2. The apparatus of claim 1 wherein said film has an emulsion on one side thereof and said compliance roll is adapted to contact the side of said film opposite said emulsion.
 3. The apparatus of claim 1 wherein said film is adapted to be indexed in a frame by frame sequence through said developing system.
 4. The apparatus of claim 3 wherein said roll is adapted to move in a direction substantially normal to the path of travel of said film.
 5. The apparatus of claim 1 wherein said compression spring comprises a helix spring member. 